Leonardo was mainly influenced by four people, Lorenzo de' Medici (Lorenzo the Magnificent), Andrea del Verrocchio, Mariano Taccola, and John Argyropoulos.
Lorenzo de' Medici was more on the political side being a patron of the arts, he was a ruler and a scholar but was passionate about Classical Antiquity, and had his own circle of humanistic values of various type, poets, artists, and philosophers.
Andrea del Verrocchio was a painter and sculptor, and a teacher to Leonardo. According to documentary proof, the only surviving painting of Verrocchio is Madonna and Child with Saints. The sculptors that Verrochio were very little, he did complete a small bronze statue of David (located in Bargello Museum, France) and Putto with Dolphin.
Mariano Taccola worked more on engines and machines, on which he left a book for each.His work was black ink on paper, had hand written annotations, and depicted many ingenious devices in milling , construction and war machinery.
John Argyropoulos was a Byzantine humanist and scholar, he worked for promoting the revival of Classical learning. He studied and earned his degree in Padua. He became a professor of Greek in Florence before moving to Rome where he continued to teach Greek until the time of his death.
Lorenzo Andrea Mariano John
http://im-possible.info/english/art/classic/mariano-taccola.html
http://www.themedicifamily.com/Lorenzo-de-Medici.html
https://www.britannica.com/biography/Andrea-del-Verrocchio
https://www.britannica.com/biography/John-Argyropoulos
http://www.themedicifamily.com/Lorenzo-de-Medici.html
https://www.britannica.com/biography/Andrea-del-Verrocchio
https://www.britannica.com/biography/John-Argyropoulos